Chapter 5: Infection Flashcards Preview

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1
Q

MC immune deficiency.

Leads to infection.

A

Malnutrition

2
Q

Microflora: stomach

A

Virtually sterile.
Some GPCs.
Some yeast.

3
Q

Microflora: proximal small bowel

A

10^5 bacteria.

Mostly GPCs.

4
Q

Microflora: distal small bowel

A

10^7 bacteria.

GPCs, GPRs, GNRs.

5
Q

Microflora: Colon

A

10^11 bacteria.

Almost all anaerobes, some GNRs, GPCs.

6
Q

MC organisms in the GI tract

A

Anaerobic bacteria (more common than aerobic bacteria in the colon 1,000:1)

7
Q

MC anaerobe in the colon

A

Bacteroides fragilis

8
Q

MC aerobic bacteria in the colon

A

Escherichia coli

9
Q

MC source of fever within 48 hours

A

atelectasis

10
Q

MC fever source 48 hours - 5 days

A

Urinary tract infection

11
Q

MC fever source after 5 days

A

Wound infection

12
Q

MCC gram negative sepsis

A

E coli

13
Q

What toxin is release in gram negative sepsis?

A

Endotoxin (lipopolysaccharide lipid A) is released.

14
Q

What does endotoxin release in gram negative sepsis?

A

Endotoxin triggers the release of TNF-alpha (from macrophages), activates complement, and activates coagulation cascade

15
Q

Insulin / glucose: early vs late gram negative sepsis

A

Early: decreased insulin, increased glucose (impaired utilization)
Late: increased insulin, increased glucose secondary to insulin resistance

16
Q

Often occurs just before the patient becomes clinically septic

A

Hyperglycemia

17
Q

Optimal glucose level in a septic patient

A

100 - 200 mg/dL

18
Q

Clostridium difficile colitis
Dx: ?
Tx: ?

A
Dx: C difficile toxin
Tx: 
Oral - vancomycin or flagyl
IV - Flagyl; lactobacillus can also help.
- Stop other antibiotics or change them
19
Q

90% of abdominal abscess have…

A

Anaerobes

20
Q

80% of abdominal abscess have…

A

Both anaerobic and aerobic bacteria

21
Q
  • Treated by drainage

- Usually occur 7-10 days after operation

A

Abscesses

22
Q

When do you need antibiotics for abscess?

A

In patients with diabetes, cellulitis, signs of sepsis, fever, elevated WBC, or who have bioprasthetic hardware (e.g. mechanical valves, hip replacements)

23
Q

Infection: % Clean (hernia)

A

2%

24
Q

Infection: % Clean contaminated (elective colon resection with prepped bowel)

A

3 - 5%

25
Q

Infection: % Contaminated (GSW to colon with repair)

A

5 - 10%

26
Q

Infection: % Gross contamination (abscess)

A

30%

27
Q

Purpose of prophylactic antibiotics

- Dosing?

A

To prevent surgical site infections

- Stop within 24 hours of end operation time, except cardiac, which is stopped within 48 hours of end operation time.

28
Q
  • Coagulase positive

- MC organism overall in surgical wound infections

A

Staphylococcus aureus

29
Q
  • Coagulase negative organism
A

Staphylococcus epidermidis

30
Q

Released by staph species in an exopolysaccharide matrix

A

Exoslime

31
Q

MC GNR in surgical wound infections

A

E coli

32
Q

MC anaerobe in surgical wound infections

  • Recovery from tissue indicates necrosis or abscess (only grows in low redox state)
  • Also implies translocation from the gut
A

B. fragilis

33
Q

How many bacteria are needed for wound infection?

A

> 10^5 bacteria.

- Less bacteria is needed if foreign body is present

34
Q

Risk factors for wound infection

A

Long operations. Hematoma or serum formation. Advanced age. Chronic disease (e.g., COPD, renal failure, liver failure, DM), malnutrition, immunosuppressive drugs.

35
Q

Surgical infections within 48 hours of procedure

A
  • Injury to bowel with leak
  • Invasive soft tissue infection - Clostridium perfringens and beta-hemolytic strep can present within hours postoperatively (produce exotoxins)
36
Q

MC infection in surgery patients

- Biggest risk factor?

A

UTI

- Biggest risk factor - urinary catheters: MC’ly - E coli

37
Q

Leading cause of infectious death after surgery

A

Nosocomial pneumonia

38
Q

What is nosocomial pneumonia related to?

A

Length of ventilation; aspiration from duodenum thought to have a role.

39
Q

MC organisms in ICU pneumonia

A
#1. S aureus
#2 Pseudomonas
40
Q

1 class of organisms in ICU pneumonia

A

GNRs

41
Q

MCC line infections

A
#1. S epidermidis
#2. S. aureus
#3. Yeast
42
Q

What central lines are at highest risk of infection?

A

Femoral lines

43
Q

% Line salvage rate with infection

A

50% line salvage rate with antibiotics; much less likely with yeast line infections.

44
Q

Diagnosis of line infection from central line culture

A

> 15 colony forming units = line infection -> need new site

45
Q
  • Beta-hemolytic Strep (group A), C perfringens, or mixed organisms
  • Usually occur in patients who are immunocompromised (DM) or who have poor blood supply.
  • Can present very quickly after surgical procedures (within hours)
A

Necrotizing soft tissue infections

46
Q

Pain out of proportion to skin findings, WBCs > 20, thin gray discharge, can have skin blistering / necrosis, induration and edema, crepitus or soft tissue gas on XR, can be septic

A

Necrotizing soft tissue infections

47
Q
  • Usually beta-hemolytic GAS
  • Overlying skin may be pale red and progress to purple with blister or bullae development.
  • Overlying skin can look normal in the early stages.
  • Thin, gray, foul-smelling drainage; crepitus.
  • Beta hemolytic GAS has exotoxin
    Tx?
A

Necrotizing fasciitis

- Tx: early debridement, high-dose penicillin, may want broad spectrum if thought to be polyorganismal

48
Q
  • Pain out of proportion to exam, may not show signs with deep infection.
  • Gram stain shows GPRs without WBCs
  • Myonecrosis and gas gangrene (common presentation)
  • Can occur with farming injuries
    Tx?
A

C. perfringens infections

- Tx: early debridement, high dose penicillin

49
Q

Pathophysiology C. perfringens infection

A

Necrotic tissue decreases oxidation-redux potential, setting up environment for C. perfringens.

50
Q

C. perfringens: toxin.

A

Alpha toxin

51
Q
  • Severe infection in perineal and scrotal area.
  • Risk factors: DM, immunocompromised stat
  • Caused by mixed organisms (GPCs, GNRs, anaerobes)
    Tx?
A

Fournier’s gangrene

Tx: early debridement, try to preserve testicles if possible; antibiotics.

52
Q

When do you need fungal coverage in infection?

A

Need fungal coverage for positive blood cultures, 2 sites other than blood, 1 site with severe symptoms, endopthalmitis, or patients on prolonged bacterial antibiotics with failure to improve.

53
Q
  • Not a true fungus.
  • Pulmonary symptoms most common; can cause tortuous abscesses in cervical, thoracic, and abdominal areas
    Tx?
A

Actinomyces

Tx: drainage and penicillin G

54
Q
  • Not a true fungus
  • Pulmonary and CNS symptoms most common
    Tx?
A

Nocardia

Tx: drainage and sulfonamides (Bactrim)

55
Q

Fungus: common inhabitant of the respiratory tract.

Tx?

A

Candida

Tx: fluconazole (some Candida resistant), anidulafungin for severe infections

56
Q

Tx: aspergillosis

A

Voriconazole for severe infections

57
Q

Tx: histoplasmosis

pulmonary symptoms usual; Mississippi and Ohio River Valleys

A

Liposomal amphotericin for severe infections

58
Q
  • CNS symptoms most common; usually in AIDS patients.

Tx?

A

Cryptococcus

Tx: Liposomal amphotericin for severe infections.

59
Q
  • Pulmonary symptoms
  • Southwest
    Tx?
A

Coccidioidomycosis

Tx: liposomal amphotericin for severe infections

60
Q

Risk factor for spontaneous bacterial peritonitis (SBP; primary)

A

Low protein (

61
Q

Organisms in primary SBP

A

Monobacterial

  • 50% E. coli
  • 30% Streptococcus
  • 10% Klebsiella
62
Q

Pathophysiology of primary spontaneous bacterial peritonitis

A

Secondary to decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascites); not due to transmucosal migration

63
Q

Cultures in primary spontaneous bacterial peritonitis

A

Fluid cultures are negative in many cases

64
Q

Dx: primary spontaneous bacterial peritonitis

A

PMNs > 500 cells/cc diagnostic

65
Q

Primary spontaneous bacterial peritonitis:
Tx?
Prophylaxis?

A

Tx: Ceftriaxone or other 3rd generative cephalosporin

Prophylaxis: fluoroquinolonges good (norfloxacin)

66
Q

What do you need to r/o in primary spontaneous bacterial peritonitis?

A

Intra-abdominal source (eg, bowel perforation) if not getting better on antibiotics or if cultures are polymicrobial
- Liver transplant not an option with active infection

67
Q
  • Intra-abdominal source (implies perforated viscus)
  • Polymicrobial (B fragilis, E coli Enterococcus MC organisms)
    Tx?
A

Secondary bacterial peritonitis

Tx: Usually need laparotomy to find source

68
Q

Exposure risk: HIV blood transfusion

A

70%

69
Q

Exposure risk: infant from positive mother with HIV

A

30%

70
Q

Exposure risk: Needle stick form HIV positive patient

A

0.3%

71
Q

Exposure risk: HIV positive Mucous membrane exposure

A

0.1 %

72
Q

HIV: helps decrease seroconversion after exposure

A

AZT (zidovudine, reverse transcriptase inhibitor) and ritonavir (protease inhibitor)

73
Q

When do you dose antivirals after HIV exposure?

A

Within 1-2 hours of exposure

74
Q

MCC for laparotomy in HIV patients

A

Opportunistic infections.
MC: CMV
2nd MC: Neoplastic disease

75
Q

MC intestinal manifestation of AIDS (can present with pain, bleeding or perforation)

A

CMV colitis

76
Q

MC neoplasm in AIDS patients (although surgery rarely needed)

A

Kaposi’s sarcoma

77
Q

MC site of lymphoma in HIV patients

A

Stomach most common followed by rectum.

78
Q

Lymphoma in HIV patients is mostly due to …. and treatment is….

A

Mostly due to non-Hodgkin’s (B cell)

Tx: chemotherapy usual, may need surgery with significant bleeding or perforation

79
Q

GIB in HIV: lower or upper more common?

A

Lower more common than upper

80
Q

HIV: cause upper GIB

A

Kaposi’s sarcoma, lymphoma

81
Q

HIV: cause lower GIB

A

CMV, bacterial, HSV

82
Q

CD4 counts

  • Normal
  • Symptomatic disease
  • Opportunistic infections
A

Normal: 800 - 1200
Symptomatic: 300- 400
Opportunistic:

83
Q
  • Now rarely transmitted with blood transfusion (0.0001%/unit)
  • 1% - 2% of population infected
  • Fulminant hepatic failure rare.
  • Interferon may help prevent development of cirrhosis
A

Hepatitis C

84
Q

Hepatitis C Percentages

  • Chronic infection
  • Cirrhosis
  • Hepatocellular carcinoma
A
  • Chronic infection: 60%
  • Cirrhosis: 15%
  • HCCa: 1-5%
85
Q

Tx: brown recluse spider bites

A

Tx: dapsone initially, may need resection of area and skin graft for large ulcers later

86
Q

Acute septic arthritis:

  • Bugs?
  • Tx?
A
  • Bugs: Gonococcus, staph, H, influenza, strep

- Tx: Drainage, 3rd generation cephalosporin and vancomycin until cultures show organisms

87
Q

Diabetic foot infections

  • Bugs?
  • Tx?
A

Bugs: Mixed staph, strep, GNRs, anaerobes
Tx: broad-spectrum antibiotics (Unasyn)

88
Q

Bug: found only in human bites, can cause permanent joint injury.
Tx?

A

Human bite

Tx: Broad-spectrum antibiotics (Augmentin)

89
Q

Bugs: found in cat and dog bites

Tx?

A

Pasteurella multocida

Tx: broad-spectrum antibiotics (Augmentin)

90
Q

MCC impetigo, erysipelas, cellulitis, folliculitis

A

Staph and strep most common

91
Q
  • Boil
  • Usually S. epidermidis or S. aureus
    Tx?
A

Furuncle

Tx: drainage +/- antibiotics

92
Q

Multiloculated furuncle

A

Carbuncle

93
Q

MCC peritoneal dialysis catheter infection

A

S. aureus and S. epidermidis

94
Q

Tx: peritoneal dialysis catheter infections

A

Tx: intraperitoneal vancomycin and gentamicin; increased dwell time and intraperitoneal heparin may help.

  • Remove catheter: peritonitis that lasts for 4-5 days.
  • Fecal peritonitis: requires laparotomy to find perforation
95
Q

Risk factors: sinusitis

A

Nasoenteric tubes, intubation, patients with severe facial fractures. Usually polymicrobial.

96
Q

Sinusitis:
CT?
Tx?

A

CT head: shows air-fluid levels in the sinus

Tx: broad-spectrum antibiotics; rare to have to tip sinus percutaneously for systemic illness

97
Q

Clippers vs razors?

A

Use clippers preoperatively instead of razors to decrease chance of wound infection